Security systems are well known in the art and commonly used to monitor various parameters of transport refrigeration units and the cargo carried therein. Such security systems provide security sensors that are configured to, for instance, determine the status of one or more doors of the transport unit and monitor the level of fuel in the transport unit. Using these sensors, it is possible to detect unauthorized access to the cargo and/or detect critical levels of fuel so as to provide the appropriate alerts and inform those responsible of the transport unit or cargo. More specifically, the data provided by the security sensors can be transmitted to a remote monitoring facility, stored at a local data recorder for later retrieval, or used by the control system to trigger an alarm if the data indicates atypical and/or unfavorable events. Although these control systems offer some level of security, there are still some significant deficiencies.
In order to effectively monitor the transport refrigeration unit and its respective cargo, existing security systems require a continuous supply of direct current (DC) power that is generally supplied by the battery of the transport vehicle or unit. As with common vehicle accessories, these control systems are typically switched to the ignition system of the transport unit such that DC power is only supplied while the engine, alternator and/or the battery of the transport unit is powered on. When the ignition is switched off, however, the power supplied to the control system as well as most other vehicle accessories is disabled. Furthermore, when the control system is disabled, its security sensors are unable to detect a fault condition in which, for example, a door has been opened without authorization. In such a way, even with such security measures, transport units are still vulnerable to theft, vandalism, and the like, when they are powered off and/or left unattended.
To compensate for such vulnerabilities, some existing control systems provide periodic monitoring while the transport unit is powered off. These control systems are configured to enter a sleep mode when the transport unit is turned off, during which the security sensor data are monitored and/or recorded at predetermined wake up intervals rather than being continuously on. However, the wake up intervals are generally long, lasting anywhere between 15 minutes to an hour, so as to conserve battery power and memory space. Any fault condition which occurs during these intervals can only be detected at the next wake up instance resulting in a delayed rather than an immediate response. Furthermore, during these long intervals, a person can easily disconnect the battery, disable power to the security sensors and access the cargo without triggering any alarm. Accordingly, while wake up circuits provide some added security, transport refrigeration units are still vulnerable to theft when they are powered off and/or unattended.
It is therefore an object of the present disclosure to provide a security device and system that overcomes such deficiencies and provides more comprehensive monitoring of a transport unit. Specifically, there is a need for a security device that is capable of continuously monitoring the key parameters of a transport refrigeration unit for extended periods of time regardless of the operational status thereof. Moreover, there is a need for a security system that can operate on reduced power and provide immediate response to a fault condition.